$width: 100px;
$color: #ffe700;
$l: left;

#box {
    div {
        width: $width;
        background-color: $color;
    }

    .#{$l} {
        color: red;
    }
}


// 循环得到从1到5 不包括5
@for $i from 1 to 5 {
    .li#{$i} {
        background-color: red;
    }
}

// 循环得到从1到5 包括5
@for $i from 1 through 5 {
    .li#{$i} {
        background-color: red;
    }
}


$bool: false;



header {
    @if $bool {
        color: red;
    }

    @if $bool {
        font-size: 20px;
    }

    @else {
        font-size: 12px;
    }

    @if $bool {
        font-size: 20px;
    }

    @else if $l =="left" {
        font-size: 12px;
    }

    @else {
        font-size: 50px;
    }

}



$k: 2;

@while $k < 10 {
    .con#{$k} {
        font-size: 12px;
    }

    $k: $k + 1;
}

@each $key in 100,200,300{
    .li#{$key}{
        width: $key;
    }
}